Hydraulic Schematic Symbols

Hydraulic Schematic Symbols

Airline Hydraulic's Main Page

Basic SymbolsLines

-continuous line - flow line

-dashed line - pilot, drain -envelope - long and short dashes around two or more component symbols.

Circular-large circle pump, motor -small circle Measuring devices -semi-circle rotary actuator

Square-one square - pressure control function -two or three adjacent squares directional control

Diamond-diamond Fluid conditioner (filter, separator, lubricator, heat exchanger)

Miscellaneous Symbols-Spring -Flow Restrictionhttp://www.airlinehyd.com/KnowledgeCenter/Symbols.asp (1 of 12)11/15/2005 9:44:31 PM


Triangle-solid Direction of Hydraulic Fluid Flow -open Direction of Pnematic flow

Pumps and CompressorsFixed Displacement hydraulic pumpunidirectional bidirectional

Variable displacement hydraulic pumpunidirectional bidirectional

Compressor

MotorsFixed displacement hydraulic motorunidirectional bidirectional

http://www.airlinehyd.com/KnowledgeCenter/Symbols.asp (2 of 12)11/15/2005 9:44:31 PM


Variable displacement hydraulic motorunidirectional -bidirectional

Pneumatic motorunidirectional -bidirectional

Rotary Actuator- hydraulic - pneumatic

CylindersSingle acting cylinder-returned by external force -returned by spring or extended by spring force

Double acting cylinders-single piston rod (fluid required to extend and retract) -double ended piston rod

Cylinders with cushions- single fixed cushon



- double fixed cushion - single adjustable cushion - double adjustable cushion

Directional Control ValvesDirectional control valve (2 ports / 2 positions)-Normally closed directional control valve with 2 ports and 2 finite positions. -Normally open directional control valve with 2 ports and 2 finite positions.

Directional control valve (3 ports / 2 positions)-Normally closed directional control valve with 3 ports and 2 finite positions. -Normally open directional control valve with 3 ports and 2 finite positions.



Directional control valve (4 ports / 2 positions)-directional control valve with 4 ports and 2 finite postions

Directional control valve (4 ports / 3 positions)-directional control valve with 4 ports and 3 finite postions *-(center position can have various flow paths)

Directional control valve (5 ports / 2 positions) Normally a pneumatic valve-directional control valve with 5 ports and 2 finite postions

Directional control valve (5 ports / 3 positions) Normally a pneumatic valve-directional control valve with 5 ports and 3 finite postions

Proportional directional control valve Electro-hydraulic servo valve-The spool positions on these valves is variable allowing for variable flow conditions.



-single-stage direct operation unit which accepts an analog signal and provides a similar analog fluid power output -two-stage with mechnical feedback indirect pilot operation unit which accepts an analog signal and provides a similar analog fluid power output

Control MethodsManual Control-general symbol (without showing the control type) -pushbutton -lever -foot pedal

Mechanical Control-plunger or tracer



-spring -roller -roller(one direction only)

Electrical Control-Solenoid (the one winding)

Pilot Operation-pneumatic -hydraulic

Pilot operated two-stage valve-Pneumatic: Sol first stage -Pneumatic: Air pilot second stage -Hydraulic: Sol first stage -Hydraulic: Hyd pilot second stage

Check valves, Shuttle valves, Rapid Exhaust valves-check valve -free flow one direction, blocked flow in other direction



-pilot operated check valve, pilot to close -pilot operated check valve, pilot to open

Shuttle valve-to isolate one part of a system from an alternate part of circuit.

Rapid exhaust valve/Pneumatic-installed close to an actuator for rapid movement of the actuator.

Pressure Control ValvesPressure Relief Valve(safety valve) normally closed- line pressure is limited to the setting of the valve, secondary part is directed to tank.

Proportional Pressure Relief



- line pressure is limited to and proportional to an electronic signal

Sequence Valve- when the line pressure reaches the setting of the valve, valve opens permitting flow to the secondary port. The pilot must be externally drained to tank. - pressure downstream Pressure Reducing valve of valve is limited to the setting of the valve

Flow Control ValvesThrottle valve-adjustable output flow

Flow Control valve



-with fixed output (variations in inlet pressure do not affect rate of flow) -with fixed output and relief port to reservoir with relief for excess flow (variations in inlet pressure do not affect rate of flow) -with variable output -fixed orifice -metered flow toward right free flow to left -pressure compensated flow control fixed output flow regardless of load -pressure and temperature compensated -with variable output and relief port to reservoir

Flow dividing valve-flow is divided equally to two outputs.



Shut-Off Valve-Simplified symbol

Accumulators

Filters, Water Traps, Lubricators and Miscellaneous ApparatusFilter or Strainer

Water Trap-with manual drain -with automatic drained

Filter with water trap-with manual drain -automatic drain

Air Dryerrefrigerant, or chemical removal of water from compressed air line

Lubricator



-oil vapor is indected into air line

Conditioning unit-compound symbol of filter, regulator, lubricator unit -Simplified Symbol

Heat Exchangers-air or water cooled unit designed to remove heat from oil returning to reservoirHydraulics| Pneumatics| Electro Controls| Marine & Mobile| Fluid Connectors| Safety Systems| Training| Repair & Field Service

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Hydraulic Schematic Symbols

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